Textile impact tester



April 2, 1963 E. P. CARTER TEXTILE IMPACT TESTER 2 Sheets-$h eet 1 Filed Feb. 19, 1960 INVENTOR. ERNEST CARTER a ATTORNEY TEXTILE IMPACT TESTER Filed Feb. 19, 1960 2 Sheets-Sheet 2 AIR 4 BLOCK souRcE TEMPERATURE CONTROL HEATER -5I Fig, 2.

J 54 v AMPLIFIER RECORDER 53 I s-r ATTORNEY United States Patent Ofitice 3,683,564 Patented Apr. 2, 1963 Th s invention relates to an apparatus and method for measuring the impact strength of textile materials. By impact strength, as used herein, there is meant that property which enables a given textile matereial to with stand or resist the stresses of shock loading.

While there are devices and procedures for evaluating the strength property of textile materials, they are not reliable for use in measuring the ability to resist impact forces. Although the strength property is involved in establishing the level of resistance to the impact process, the conditions of impact are different from those which prevail in the usual strength tests. For example, conventional strength tests are conducted with relatively low loading rates while the impact process is characterized by an extremely fast loading rate. It is primarily for this reason that standard strength tests cannot properly be employed for measuring impact strength in that the load which textile yarns and cords are able to sustain without breaking varies with the rate of load application. Moreover, the order or rank of dififering textile materials based on load sustaining ability has been found to differ with a change in the rate of loading.

Because textile materials, such as nylon, rayon and the like have been employed with increasing frequency in the fabrication of products where resistance to shock loading is an essential service requirement, a need has developed for means to accurately evaluate the ability of textiles to withstand these stresses. That is, it has become necessary to properly evaluate the impact resistance of textiles which are contemplated for use in the fabrication of such products as the structural elements of pneumatic tires, parachute guide lines, tow ropes, various types of netting and the like.

Accordingly, it is a primary object of this invention to provide a means for accurately evaluating the impact strength of textile materials.

It is a further object of this invention to provide a device capable of applying a shock load to a textile test specimen, sufficient to break it, and to indicate the energy required to effect the break or rupture.

Other objects and advantages of the present invention will become apparent in the description as given hereinafter.

in general, the objects of this invention are accomplished by a device having means provided for (l) suspending a textile filament at a predetermined tension, (2) applying an impact force to the suspended and tensioned test specimen suflicient to effect the rupture thereof, and (3) indicating the energy absorbed from the applied force to accomplish this rupture.

An essential element of the test device is a Weighted pendulum which provides the means for shock loading the suspended test specimen. The pendulum is adapted to be released from a poised position at a predetermined angle of deflection from the vertical such that it will strike the test specimen laterally at the bottom of its swing in free-fall with sufiicient force to break it. The relative amount of kinetic energy absorbed from the free-falling pendulum in effecting the break or rupture of the test specimen affords a measure of the impact resistance property.

The amount of energy absorbed from the swinging pendulum in causing the test filament to break is determined by comparing the angular deflection of the pendulum after passing through the equilibrium position at the bottom of its swing without a test specimen in place against the instance where a test specimen is in place and intelposed as an obstruction in the swing path of the pendulum. Thus, the energy absorbed from the freefalling pendulum in effecting rupture of the test speci men is given by the relation V=MXg (cos 0cos 0 where M represents the total pendulum mass, X is the distance from the axis of suspension of the pendulum to its center of gravity, where g is the acceleration of gravity, 0 is the angle of deflection of the pendulum from the vertical after rupturing the test specimen, and H is the angle of deflection of the free-falling pendulum Without a test specimen in place. Error due to extraneous frictional losses (bearings, wind resistance, etc.) is eliminated from consideration on the plausible assumption that these small losses are constant both with and Without a test specimen in place and therefore cancel out.

As is clearly evident, it is essential that angular deflections of the'pendulum be capable of a very precise measurement since comparative differences Will always be small in view or the low energy requirement for breaking a single filament test specimen. Hence, a particularly important feature of the present invention, as will be described hereinafter, is the provision of highly sensitive indicating means for accurately measuring the arc traversed by the pendulum as it swings from free-fall in a test situation.

Since it is desirable in some instances to have the test specimen at a controlled elevated temperature when applying the impact force, means are provided for accomplishing this objective. The capability for conducting the impact test at an elevated temperature is particularly important when testing textile tire cord in that the pneumatic tires of motor vehicles experience temepratures of C. or better during service, and it has been found that elevated temperaures afiect impact performance. Thus, in order to obtain test data having a closer correlaion with actual service experience, it is necessary to simulate the temperatures encountered in service.

The above-noted and other elements of the present invention are described in greater detail in the discussion which follows wherein reference is made to the accompanying drawing which illustrates a preferred embodiment. Because the drawing is presented merely to illustrate a particular embodiment of this invention, it should in no way be considered as limitative.

In the drawing,

FIGURE 1 is a perspective view of a preferred embodiment of the invention illustrating the general layout of that part of the apparatus which includes the pendulum and the means for suspending the test specimen at a predetermined tension.

FIGURE 2 is a schematic diagram of the various elements which can be used to bring the test specimen to a predetermined elevated temperature.

FIGURE 3 is a schematic diagram of the circuit employed to measure and record the angular displacement of the pendulum in a test situation.

Referring to the drawing, the numeral 10 designates a base member. Extending upwardly from the base It) is a supporting standard 11 having a horizontal extension 13 at the end of which there is mounted a housing 16. Protruding out longitudinally from housing 16 is a shaft 15 which is mounted on ball hearings to permit free rotation thereof. Pivotally connected to shaft 15 is a weighted pendulum l2.

Pendulum 12 is held in poised position at a predetermined angle from the vertical by a spring loaded pin 21. Pin 21 is horizontally mounted at the upper end of slotted bar 19 which in turn is secured within bracket support 26 along with disc 18 by means of Wing nut 22. The angle at which the slotted bar it? is positioned can be modified by loosening wing nut 22 and adjusting the bar to the desired angle. Since the slotted bar 1? supports the pin 21 against which the pendulum rests when held in poised position, any change in the angle at which the bar is held will cause a like change in the initial deflection of the pendulum, i.e. the angular displacement from the vertical at which the pendulum is held prior to release for a free-fall swing. Thus, the pendulum can be initially poised at any deflection up to 90 for differing test situations by referring to the calibrations on disc 13 for the desired angle and adjusting bar 19 accordingly. The mechanism by which the pendulum is released from its poised position to swing in free-fall is by the longitudinal displacement of that part of pin 21upon which the pendulum rests. Since the pin 21 is spring loaded, this is accomplished by manually forcing the pin in a direction opposing the spring bias.

Mounted in the test block 24 are test specimen clamps 25 and 26, positioned between clamps 25 and 26 and in alignment therewith are cylindrical posts 27 and 28. These cylindrical structures provide smooth, rounded surfaces for the test filament to bend aga nst upon receiving the pendulum impact and prevent tearing of the test specimen which might other-Wise occur if bending took place at the sharp clamp surfaces. Between cylindrical posts 27 and 23 there is a groove 29 in the test block 24 which extends across the width thereof. The purpose of this groove is to provide a means for the pendulum to pass through the block 24 while swinging from free-fall.

In alignment with clamps 25 and as but positioned outside the test block 24, there is shown a means for imparting predetermined tension to the test filament 30 which includes a supporting base 31 having an upright 32 extend ing vertically therefrom. Secured to the upper end of the upright 32 and extending out horizontally therefrom is a stationary shaft 33 having a sleeve 34 rotatably mounted thereon. Rigidly attached to sleeve 34 and adapted to pivot in opposition to each other are lever arms 3-5 and 36. Attached to the free end of lever arm 35. is a grooved member 37 to which one end of the test specimen is secured. That is, one end of the test specimen is wound in the groove of member 37 and secured therein by tightening lock nut 33. An adjustable counter-weight 39 a is attached to lever arm 3d and is adapted for positioning anywhere along the length thereof. Thus, the tension on the test specimen can be controlled by position adjustment of counter-weight 39 on lever arm 36.

vAs has been indicated, it is often desirable that the test specimen be at a controlled, elevated temperature while conducting the impact strength test, with such condition being particularly desirable when testing textile materials which are contemplated for a tire cord end use. Reference is made to the schematic diagram of FIGURE 2 where a suitable arrangement of means for heating and for controlling the temperature of the test block are illustrated. Thus, there is shown a heating means 51 and temperature control means 52 connected to each other with both being in turn connected to the test block 24- at different points thereon. The heating means may comprise any suitable, commercially available, electrically operated heating device. The heat source may be positioned outside the test block or alternatively electrical heating elements can be insertedwithin the block. The temperature control means employed can be any of the well-known devices normally used for this purpose, such as an electrically'operated standard bridge type temperature control. In order to restrict entry of unheated air into the test block, air pressure is maintained therein which exceeds that of the atmosphere. Thus, as is shown in FIGURE 2, a source of compressed air 58 is connected i to both ends of the test block 24. Metal tubing or any other suitable conduit may be used to transfer compressed air into the block from an outside source.

shown in FIGURE 1) which also prevent heat losses from the block. The cover members are provided with handles 42 and 43 to facilitate the opening and closing thereof. In order that the covermembers can be made to close properly over clamps 25 and 26 as well as cylindrical posts 27 and 28 which protrude above the top surface of the test block 24, recesses such as 25a and 27a are pro vided in both cover members. Since it is desirable that there be a uniform distribution of heat throughout the testing block when employing elevated temperatures during the testing operation, the inside surfaces of block 24 and cover members 40 and 4-1 are preferably lined with a heat conducting material such as aluminum. it is also desirable that the block and cover members he insulated with asbestos or other insulating material to further minimize loss of heat therefrom.

As explained hereinabove, the impact strength of textile materials is evaluated in accordance with the procedure of this invention by determining the amount of energy absorbed from the'free-falling pendulum in effecting a rupture of the test specimen, which is generally a single textile filament. from the pendulum to break the test filament, it is necessary that an accurate measurement of the angular deflection experienced by the pendulum in each test run he obtained.

Since the pendulum :12. is pivotally connected to rotatable shaft 15, this shaft is caused to rotate in response to the pendulum swing. The degree or extent or rotation will, of course, correspond directly to the angular displacement or the arc traversed by the pendulum a it is allowed to swing from free-fallin a test situation. Thus, the angular displacement of the pendulum can be readily ascertained from a measurement of the torque produced in shaft 15 through movement of the pendulum 12. This measurement is obtained in the present invention by employing a low-torque potentiometer which is connected to rotatable shaft 15 and accurately divides an electric current or voltage inproportion to the shaft rotation. The potentiometer is mounted in the housing 16 shown in FIGURE 1 as is shaft 15 to which it is connected. It is necessary to employ a potentiometer having a low torque requirement because of the light radial loads to which this instrument must respond. However, any commercially available potentiometer having a torque requirement in the range of from about 0.003 to 0.008 o'z./inch can be suitably employed.

Reference is made to FIGURE 3 of the drawing where aschematic diagram is shown of the circuit contemplated for indicating and recording the rotation of the shaft to which the pendulum 12 is connected, such as shaft 15 in FIGURE 1. There is shown a power source 53 and a standard potentiometer circuit including a coil 54 and coil tap 55 connected thereto. The coil tap 55 is caused to move and divide the current or voltage in response to the swinging movement of pendulum 12. which is connected to the coil tap through a horizontal rotatable shaft, such as shaft 15, as shown in FTGURE 1. This induces an electrical signal in the potentiometer circuit which passes to an amplifier 56 and finally to an electrical recorder 57. The amplifier used may be any of the standard types while the electrical recorder may, for example, be a strip recorder or any other type conventionally used for such purpose.

The procedure generally followed when employing the impact testing device :of this invention is to first adjust the pendulum holding means to obtain the desired initial angular deflection of the pendulum before it is released for free-fall. This is accomplished by loosening wing nut 22 so that slotted bar 1% can be properly positioned to the desired angle using the angle calibrations on disc +18 The test block is provided with hinged cover members 40 and 41 (as- In determining the energy absorbed as a guide. After adjustment of the pendulum holding means, the pendulum is released from the initial deflection at which it is held to swing in free-fall over an unobstructed path, i.e., without a test specimen in the swing path, and the arc traversed is ascertained and recorded. Following a determination of the angle displaced by the pendulum when free to swing in an unobstructed path, the test specimen is positioned in the swing path and the angle displaced by the pendulum is again determined with the test filament obstructing the sw ng path. This angle will, of course, be smaller than in the instance where the path of the pendulum was unobstructed, since breaking the test filament will consume gravitational energy. The extent of difference in the magnitude of these angles affords the measure of impact resistance possessed by the test specimen.

It is to be understood that the above-described embodiment of this invention is amenable to many modifications. Consequently, the intent is to cover all such changes and modifications which do not constitute departures fromthe spirit and scope of the invention as set forth in the following appended claims.

I claim:

1. A device for testing the capacity of a textile filament for resisting rupture from impact loading comprising: a base, a block supported on the base, said block being provided with a central groove extending across the width thereof and hinged cover members, a pair of filament positioning clamps mounted within said block on opposite sides of the central groove thereof, tension regulating means mounted adjacent said filament positioning clamps for maintaining a predetermined tension on said filament, means for maintaining the filament at an elevated predetermined temperature, a rotatable shaft mounted above the base, a weighted pendulum secured to the rotatable shaft and adapted to swing in a path wherein engagement is made with the filament to effect a rupture thereof, a releasable support for positioning the pendulum at a predetermined angle from the vertical, an electrical power source, a potentiometer connected across the power source and having a coil tap secured to the rotatable shaft so that movement of the pendulum moves said coil tap, and means for indicating the movement of the coil tap.

2. A device for testing the capacity of a textile filament for resisting rupture from impact loading comprising: a base, a block supported on the base, said block being provided with a central groove extending across the width thereof and hinged cover members, a pair of filament positioning clamps mounted within said block on opposite sides of the central groove thereof, tension regulating means mounted adjacent said filament positioning clamps for maintaining a predetermined tension on said filament, an electrically operated heater connected to said block, an electrically operated temperature control device connected to said heater and to said block, a rotatable shaft mounted above the base, a weighted pendulum secured to the rotatable shaft and adapted to swing in a path wherein engagement is made with the filament to effect a rupture thereof, a releasable support for positioning the pendulum at a predetermined angle from the vertical, an electrical power source, a potentiometer connected across the power source and having a coil tap secured to the rotatable shaft so that movement of the pendulum moves said coil tap, and means for indicating the movement of the coil tap.

3. A device for testing the capacity of a textile filament for resisting rupture from impact loading comprising: a base, a block supported on the base, said block being provided with a central groove extending across the width thereof and hinged cover members, a pair of filament positioning clamps mounted within said block on opposite sides of the central groove thereof, a pair of cylindrical posts positioned within the block on either side of the central groove thereof and between said filament positioning clamps, tension regulating means mounted adjacent said filament positioning clamps for maintaining a predetermined tension on said filament, means for maintaining the filament at an elevated predetermined temperature, a rotatable shaft mounted above the base, a weighted pendulum secured to the rotatable shaft and adapted to swing in a path wherein engagement is made with the filament to efiect a rupture thereof, a releasable support for positioning the pendulum at a predetermined angle from the vertical, an electrical power source, a potentiometer connected across the power source and having a coil tap secured to the rotatable shaft so that movement of the pendulum moves said coil tap, and means for indicating the movement of the coil tap.

4. A device for testing the capacity of a textile filament for resisting rupture from impact loading comprising: a base, a block supported on the base, said block being provided with a central groove extending across the width thereof and hinged cover members, a pair of filament positioning clamps mounted within said block on opposite sides of the central groove thereof, tension regulating means mounted adjacent with said filament positioning clamps for maintaining a predetermined tension on said filament, an electrically operated heater connected to said block, an electrically operated temperature control device connected to said heater and to said block, a source of compressed air connected to said block, a rotatable shaft mounted above the base, a weighted pendulum secured to the rotatable shaft and adapted to swing in a path wherein engagement is made with the filament to effect a rupture thereof, a releasable support for positioning the pendulum at a predetermined angle from the vertical, an electrical power source, a potentiometer connected across the power source and having a coil tap secured to the rotatable shaft so that movement of the pendulum moves said coil tap, and means for indicating the movement of the coil tap.

References Cited in the file of this patent UNITED STATES PATENTS 1,946,100 Norton Feb. 6, 1934 2,521,244 Moore Sept. 5, 1950 2,778,219 Wachter Jan. 22, 1957 OTHER REFERENCES Publication: Textile Research Journal, December 1953, Article by Lyons et al., pages 917-925. (Copy in 73-12.)

Publication: Symposium on Impact Testing, ASTM #176 (1956), pages 134139. (Copy in Scientific Library TA407 A5i.) 

1. A DEVICE FOR TESTING THE CAPACITY OF A TEXTILE FILAMENT FOR RESISTING RUPTURE FROM IMPACT LOADING COMPRISING: A BASE, A BLOCK SUPPORTED ON THE BASE, SAID BLOCK BEING PROVIDED WITH A CENTRAL GROOVE EXTENDING ACROSS THE WIDTH THEREOF AND HINGED COVER MEMBERS, A PAIR OF FILAMENT POSITIONING CLAMPS MOUNTED WITHIN SAID BLOCK ON OPPOSITE SIDES OF THE CENTRAL GROOVE THEREOF, TENSION REGULATING MEANS MOUNTED ADJACENT SAID FILAMENT POSITIONING CLAMPS FOR MAINTAINING A PREDETERMINED TENSION ON SAID FILAMENT, MEANS FOR MAINTAINING THE FILAMENT AT AN ELEVATED PREDETERMINED TEMPERATURE, A ROTATABLE SHAFT MOUNTED ABOVE THE BASE, A WEIGHTED PENDULUM SECURED TO THE ROTATABLE 